1. Field of the Invention
This invention relates to butyl rubber compositions exhibiting improved adhesion to polyester textile materials.
2. Description of Related Art
Polyester textiles have long been used as reinforcing agents for rubber articles such as pneumatic tires, hoses, V-belts, air springs and the like. As used in the description of the invention following the term "polyester textile" or "polyester textile material" refers to any filament, fiber thread, yarn, cord, cable, woven fabric, nonwoven fabric, knit fabric or the like, fabricated in whole or part from a synthetic, high molecular-weight polymer in which the major portion by weight has been derived from the condensation of a polybasic acid and a polyhydric alcohol which has a high degree of modulus and tensile strength and imparts to manufactured rubber articles in which it is incorporated, form and structure and/or a high degree of strength, toughness and durability. The polyester polymers normally employed in textiles are derived from the condensation of an aromatic acid, usually a phthalic acid or a low molecular weight diester thereof, and a low molecular weight glycol, such as ethylene glycol or 1,4-dimethylol cyclohexane. A particularly preferred polyester textile is polyethylene terephthalate because of the many desirable properties it imparts to textiles such as high modulus and tensile strength, high melting point, resistance to flexing, dimensional stability and resistance to degradation and loss of properties upon exposure to environmental conditions of use.
However, in spite of the foregoing numerous advantages of polyester textile, their use as a reinforcement for rubber articles such as pneumatic tires, belts, hose, air springs, and the like has been seriously impeded because the adhesion of polyester textile to elastomers is, in general, very poor. Apparently the polyester textile is so inert chemically, compared to rayon and nylon which contain many more reactive groups in their chains, that there is little or no tendency for the polyester textile to form a strong adhesive chemical bond with elastomers when the usual adhesives are used. The problem of adequate adhesion of polyester textile is especially important in the case of butyl rubber, which has many desirable characteristics that would enable composite articles made of butyl rubber, reinforced with polyester textile, to serve many purposes in an improved manner.
An especially important application for reinforced butyl rubber (isobutylene-isoprene copolymer rubber) and particularly halogenated butyl rubber, is in the construction of hoses and tubing for use in automotive and air conditioning applications. Butyl rubber has outstanding impermeability to water vapor and many organic solvents, including fluorinated hydrocarbons, with which it comes into contact. This property renders polyester textile-reinforced butyl rubber an ideal candidate for applications such as water hoses, hydraulic brake lines, air-conditioning hoses and the like.
Numerous approaches have been taken in the prior art to improve the adhesion of polyester textile to elastomers such as butyl rubber. U.S. Pat. No. 2,561,215 discloses coating the textile with a rubber latex containing a resorcinol/formaldehyde type adhesive or adhesives based on copolymers containing vinyl pyridine or pyrrolidones. According to U.S. Pat. No. 3,036,948, polyester textiles treated with epoxy resins exhibit improved adhesion to butyl rubber which contains 2,2'-methylene-bis-(4-chloro-6-methylolphenol) as a curing auxiliary. Adhesion of polyester textile to elastomers is enhanced according to U.S. Pat. No. 3,449,200 by first coating the textile with a composition based on a mixture of an aldehyde type resin and a polyethylenimine.
While these and other techniques for improving adhesion have proven successful to varying degrees, there is a need in the art for improved approaches to solving the adhesion problem which are more simple, which do not require the use of noxious chemicals or elastomer additives which may detract from the physical and chemical properties of the cured rubber, and which provide for enhanced adhesion.